With conventional techniques, a lane departure warning apparatus is known, which is configured to monitor a traffic lane by means of a vehicle-mounted camera, and to issue a warning when the vehicle departs from the traffic lane. For example, a lane departure warning apparatus is described in Patent document 1, which is configured to estimate the probability of departure of the user's vehicle from the driving lane by means of a lane monitoring camera that acquires an image of the road surface, and to instruct a warning unit to issue a warning when judgment is made that the probability of departure of the user's vehicle from the traffic lane becomes high.